Conventionally, the manufacture of such products involves preparing an absorbent pad that will be sandwiched normally between a permeable inner layer of non-woven fabric and an impermeable outer layer of polyethylene.
In the case of nappies and incontinence pads (baby and adult diapers), the pad consists in a mass of cellulose fibres that is suitably shaped and preformed, then interposed between the two aforementioned layers.
More exactly, devices of conventional type for making the pads in question utilize bands of compacted cellulose wound previously into rolls. These bands of material are fed to suitable grinding means by which the compacted cellulose is broken down into an incoherent mass of cellulose fibres, or fluff.
The fibres generated in this way are conveyed toward aspirating cavities negatively reproducing the required shape of the pad, and held together with the aid of aspirating means by which a partial vacuum is created in the selfsame cavities.
The shape of the aspirating cavities is dictated by the fact that the pads of the baby and adult sanitary items in question must present an exact geometry. In these products, more exactly, the central portion of the pad must have an absorbent capacity distinctly higher than that of the peripheral portion. Accordingly, the pads must be fashioned in such a manner that the central portion will be much thicker than the peripheral portion.
Once the pad has been prepared in this way, it is placed between the inner and outer layers.
Disadvantageously, the devices and the methods employed hitherto to make the pads in question are decidedly complex, and do not always deliver correct and dependable results.
In effect, preparation of the pads by the method described above involves holding together an incoherent mass of fibres that tend easily to scatter, with the result that the shape of the pad is lost.
This creates significant problems, deriving both from the notable amount of fluff dust produced, and the fact that considerable precautions are needed to keep the pad stable.
Furthermore, it is not unusual for the aspirating cavities to be filled either incompletely or erratically during the process of forming the pads, with a considerable number of defective items consequently having to be discarded.
Prior art methods of manufacturing other related items, such as sanitary napkins for women, now include the use of pads prepared from bands of an already formed and stable absorbent material, wound into rolls. In this instance the pads are prepared by cutting portions of the required shape from the continuous band.
However, the bands in question are of constant thickness and this precludes their use in the manufacture of nappies for babies and incontinence pads for adults, as they cannot guarantee a correct differentiation between the absorbent capacities at the centre and at the periphery of the pad.